Recording apparatus

ABSTRACT

Disclosed is a recording apparatus that helps to achieve a reduction in size and cost. The recording apparatus has a U-turn sheet feeding mechanism for reversing and feeding a recording medium and a duplex transport mechanism for reversing the recording medium and performing printing on both sides thereof, in which the same transport path serves as a transport path for transporting the recording medium from a U-turn sheet feeding roller to a main transport roller for transporting the recording medium to a printing portion and as a transport path for reversal in duplex transport. Further, a transport roller provided in the transport path from the U-turn sheet feeding roller to the main transport roller for transporting the recording medium to the printing portion is the same as a transport roller for duplex transport. A single transport roller serves both as the U-turn transport roller and as the duplex transport roller.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a recording apparatus that performsrecording on a recording sheet by a recording means.

2. Related Background Art

A conventional recording apparatus will be described with reference toFIG. 24.

In FIG. 24, reference numeral 901 indicates a recording head thatperforms recording by selectively discharging ink from a plurality ofdischarge ports. The recording head 901 is retained in position by acarriage (not shown), and reciprocates in a direction perpendicular tothe conveying direction of a recording medium, thereby performingprinting on the recording medium. Reference numeral 902 indicates aplaten opposed to the recording head, and retains the recording mediumat a printing portion.

Next, a U-turn feeding structure will be described.

Reference numeral 905 indicates a sheet feeding cassette that retainsrecording mediums in a stacked state, reference numeral 906 indicates aU-turn sheet feeding roller for separately conveying the recordingmediums, reference numeral 910 indicates a paper guide on the inner sideof a U-turn portion, reference numeral 911 indicates a paper guide onthe outer side of the U-turn portion, reference numeral 907 indicates aU-turn transport roller, reference numeral 908 indicates a U-turntransport roller adapted to be driven to rotate while pressurizing theU-turn transport roller 907, reference numeral 903 indicates a transportroller pair for transporting the recording medium to a printing portion,reference numeral 913 indicates a paper guide for guiding the recordingmedium to the transport roller pair 903, reference numeral 904 indicatesan ejection roller pair for ejecting the recording medium, and referencenumeral 909 indicates an ejection tray retaining the ejected recordingmedium. Reference numeral 912 indicates a U-turn paper guide flapper forswitching between U-turn transport and reversal transport for two-siderecording.

Next, a U-turn sheet feeding operation will be described.

The recording mediums stacked in the sheet feeding cassette 905 areseparately transported in the direction of the arrow M by the U-turnsheet feeding roller 906, further transported in the direction of thearrow N by the U-turn transport roller 907 and the U-turn transportroller 908, and transported in the direction of the arrow P while guidedby the paper guides 910, 911, and 913. At this time, the U-turn paperguide flapper 912 moves in the direction of the arrow Q (indicated bythe dashed line) to secure the U-turn transport path. Next, therecording medium is transported to the printing portion by the transportroller pair 903, and printing is effected by the recording head 901.Then, the recording medium is transported in the direction of the arrowU by the ejection roller pair 904, and ejected onto the ejection tray909.

Next, a two-side printing structure will be described.

Reference numerals 914 and 915 indicate duplex transport rollers,reference numeral 916 indicates duplex transport rollers adapted to bedriven to rotate while pressurizing the duplex transport rollers 914 and915, reference numeral 917 indicates outer paper guides for duplextransport, reference numerals 918 and 919 indicate inner paper guidesfor duplex transport, and reference numeral 920 indicates a two-sidepaper guide flapper for switching the transport path before and afterreversal in duplex transport.

Next, a two-side printing operation will be described.

Printing is performed by the recording head 901 on the recording mediumfed by the U-turn sheet feeding mechanism; when the printing on theobverse side is completed, the transport roller pair 903 and theejection roller pair 904 are reversed in rotation to transport therecording medium in the direction of the arrow R. The recording mediumis further transported in the direction of the arrow S by the transportroller pair 903, and transported to a duplex transport portion. At thistime, the U-turn paper guide flapper 912 moves in the direction of thearrow T, and the two-side paper guide flapper 920 moves in the directionof the arrow K, securing the transport path for the recording medium inthe direction of the arrow S.

Further, the recording medium is transported by the duplex transportrollers 914 and 915 and the duplex transport rollers 916, and guided bythe paper guides 917, 918, and 919 to be transported in the directionsof the arrows H and I. The recording medium is transported again in thedirection of the arrow P toward the transport roller pairs 903 in areversed state. At this time, the two-side paper guide flapper 920 movesin the direction of the arrow L (indicated by the dashed line), securingthe transport path after reversal. Printing is performed on the reverseside of the reversed recording medium by the recording head 1, and, whenthe printing is completed, the recording medium is ejected onto theejection tray 909, thereby completing the two-side printing.

The above-described conventional example has the following problems.

Since the paper transport path is independent, mounting of the U-turnsheet feeding mechanism and the two-side printing mechanism results inan increase in the size of the apparatus main body in height directionand depth direction, thus hindering achievement of a reduction in size.Further, the provision of the independent transport mechanism leads toan increase in cost, which means the construction cannot be adopted inan inexpensive apparatus.

Further, to cope with jamming due to defective transport of a recordingmedium, it is necessary to provide a mechanism allowing opening of thepaper guide portion; in this case also, the transport mechanism isindependent, and the paper guide portion opening mechanism is alsoformed separately, which leads to an increase in apparatus size andcost.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a recordingapparatus that helps to achieve a reduction in size and cost.

It is another object of the present invention to provide a recordingapparatus comprising:

a U-turn sheet feeding roller for reversing and feeding a recordingmedium; a main transport roller for transporting the recording medium onan upstream side of a recording head; a reversing mechanism for turningthe recording medium upside down; a first transport path fortransporting the recording medium from the U-turn sheet feeding rollerto the main transport roller; a second transport path for transportingthe recording medium in the reversing mechanism, the second transportpath sharing a portion thereof with the first transport path; and athird transport path arranged in the portion shared by the first andsecond transport paths and adapted to transport a recording medium ofhigh rigidity.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a sectional view of the main body of a recording apparatusaccording to Embodiment 1 of the present invention;

FIG. 2 is a sectional view of a driving portion of the recordingapparatus according to Embodiment 1 of the present invention;

FIG. 3 is a sectional view of the driving portion of the recordingapparatus according to Embodiment 1 of the present invention;

FIG. 4 is a perspective view of the recording apparatus according toEmbodiment 1 of the present invention;

FIG. 5 is a sectional view of the main body of a recording apparatusaccording to Embodiment 2 of the present invention;

FIG. 6 is a sectional view of the main body of the recording apparatusaccording to Embodiment 2 of the present invention;

FIG. 7 is a sectional view of the main body of a recording apparatusaccording to Embodiment 3 of the present invention;

FIG. 8 is a sectional view of the main body of the recording apparatusaccording to Embodiment 3 of the present invention;

FIG. 9 is a sectional view of the main body of a recording apparatusaccording to Embodiment 4 of the present invention;

FIG. 10 is a sectional view of the main body of the recording apparatusaccording to Embodiment 4 of the present invention;

FIG. 11 is a sectional view of the main body of a recording apparatusaccording to Embodiment 5 of the present invention;

FIG. 12 is a sectional view of the main body of the recording apparatusaccording to Embodiment 5 of the present invention;

FIG. 13 is a sectional view of a driving portion of a recordingapparatus according to Embodiment 6 of the present invention;

FIG. 14 is a sectional view of a driving portion of the recordingapparatus according to Embodiment 6 of the present invention;

FIG. 15 is a sectional view of the main body of a recording apparatusaccording to Embodiment 8 of the present invention;

FIG. 16 is a sectional view of the main body of a recording apparatusaccording to Embodiment 9 of the present invention;

FIGS. 17A and 17B are sectional views of a U-turn transport portion;

FIG. 18 is a schematic explanatory view of a duplex transport path and aU-turn sheet feeding transport path;

FIG. 19 is a sectional view showing how a thick recording medium, suchas a CD or DVD, is transported;

FIG. 20 is an explanatory view of a drive row from a drive motor to aU-turn transport roller;

FIGS. 21A and 21B are explanatory views of a drive system;

FIGS. 22A, 22B, and 22C are diagrams illustrating how a recording mediumis transported;

FIGS. 23A and 23B are diagrams illustrating how duplex transport isperformed; and

FIG. 24 is a sectional view of the main body of a conventional recordingapparatus.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

In the following, embodiments of the present invention will be describedwith reference to the accompanying drawings.

[Embodiment 1]

Embodiment 1 of the present invention will be described with referenceto FIGS. 1 through 4. FIG. 1 is a main body sectional view showingEmbodiment 1, FIGS. 2 and 3 are main body sectional views showing adrive construction, and FIG. 4 is a perspective view showing how a thickrecording medium, such as a CD or DVD, is transported.

In FIG. 1, reference numeral 1 indicates a recording head thatdischarges ink selectively from a plurality of discharge ports toperform recording. The recording head 1 is retained in position by acarriage (not shown), and reciprocates in a direction perpendicular tothe recording medium transporting direction to perform printing on arecording medium. Reference numeral 2 indicates a platen opposed to therecording head 1 and retains the recording medium at a printing portion.

Next, a U-turn sheet feeding structure will be described.

Reference numeral 5 indicates a sheet feeding cassette retainingrecording mediums in a stacked state, reference numeral 6 indicates aU-turn sheet feeding roller for separately transporting the recordingmediums, reference numeral 23 indicates a paper guide for guiding theouter side of the recording medium at the time of U-turn sheet feedingand at the time of duplex transport, reference numeral 21 indicates aU-turn transport roller for transporting the recording medium at thetime of U-turn sheet feeding and at the time of duplex transport,reference numeral 25 indicates a U-turn transport roller adapted to bedriven to rotate while pressurizing the U-turn transport roller 21,reference numeral 3 indicates a main transport roller pair fortransporting the recording medium to the printing portion, referencenumeral 26 indicates a paper guide for guiding the recording medium tothe main transport roller pair 3, reference numeral 4 indicates anejection roller pair for ejecting the recording medium, and referencenumeral 9 indicates an ejection tray for retaining the ejected recordingmedium. Reference numeral 24 indicates a paper guide flapper weaklyurged in the direction of the arrow K, using a portion 24B as therotation center, to abut the paper guide 26. The paper guide flapper 24guides the inner side of the recording medium at the time of U-turnsheet feeding and at the time of duplex transport.

Next, a U-turn sheet feeding operation will be described.

The recording mediums stacked in the sheet feeding cassette 5 areseparately transported in the direction of the arrow M by the U-turnsheet transport roller 6, further transported in the direction of thearrow by the U-turn transport roller 21 and U-turn transport rollers 25,and transported in the direction of the arrow I while guided by thepaper guide 26 and the paper guide flapper 24. At this time, therecording medium is urged with low pressure toward the paper guideflapper 24 and the paper guide 26, so that it can pass between the paperguide 26 and the paper guide flapper 24. The recording medium is furthertransported in the direction of the arrow P to the printing portion bythe main transport roller pair 3, and printing is performed thereon bythe recording head 1; the recording medium is then transported in thedirection of the arrow U by the ejection roller pair 4, and ejected ontothe ejection tray 9.

Next, a two-side printing structure will be described.

Reference numerals 22 and 27 indicate paper guides for guiding the outerside of the recording medium at the time of duplex transport. The paperguide flapper 24 has a guide portion 24A for guiding the inner side ofthe recording medium at the time of duplex transport.

Next, a two-side printing operation will be described.

The recording medium fed by the U-turn sheet feeding mechanism undergoesprinting by the recording head 1; when the printing on the obverse sideis completed, the main transport roller pair 3 and the ejection rollerpair 4 are reversed in rotation to transport the recording medium in thedirection of the arrow R. The recording medium is further transported inthe direction of the arrow S by the main transport roller pair 3, andtransported to a duplex transport portion. At this time, the recordingmedium is transported while guided by the paper guide portion 24A of thepaper guide flapper 24 and the paper guide 27.

Further, while guided by the paper guide 27, the recording medium istransported in the direction of the arrow H, effecting joining with theU-turn sheet feeding transport path. The transport from this onward isthe same as that at the time of U-turn sheet feeding, the recordingmedium being transported in the directions of the arrows N and I. In areversed state, the recording medium is transported again in thedirection of the arrow P toward the main transport roller pair 3.Printing is performed on the reverse side of the reversed recordingmedium by the recording head 1; after the completion of the printing,the recording medium is ejected onto the ejection tray 9, thuscompleting the two-side printing.

Next, the construction of a horizontal path for performing printing on athick printing medium, such as a CD or a DVD, will be described withreference to FIGS. 1 through 4.

The paper guide 23 for guiding the outer side of the recording medium atthe time of U-turn sheet feeding and at the time of duplex transport isequipped with a guide hole 23B for guiding the recording medium in thehorizontal path.

The paper guide portion 24A of the paper guide flapper 24 is arrangedoutside the region where a thick recording medium is transported in thehorizontal path. In the horizontal path, the thick recording medium istransported while guided by the paper guide 24. Further, as shown inFIG. 4, when transported, a thick recording medium 55, such as a CD or aDVD, is set in position on a transport tray 54. The U-turn transportroller 21 is composed of a roller shaft 21A and rubber portionsseparately arranged thereon, with the rubber portions being arrangedoutside the region where the thick recording medium is transported inthe horizontal path. Due to this construction, the transport tray 54 canoverlap the U-turn transport roller 21 during transport.

Next, the transport operation in the horizontal path will be described.

In FIG. 1, the transport tray 54 with the recording medium 55 consistingof a CD, DVD or the like placed thereon is inserted from the ejectionside in the direction of the arrow J, and transported in the directionof the arrow R by reverse operation of the ejection roller pair 4 andthe main transport roller pair 3. Further, the transport tray istransported in the direction of the arrow V while guided by the paperguides 26, 27 and the paper guide flapper 24 to reach the guide hole 23Bof the paper guide 23. Next, the main transport roller pair 3 and theejection roller pair 4 are caused to make normal rotation to transportthe transport tray 54 in the direction of the arrow P. At this time,recording head 1 performs printing on the recording medium 55, such as aCD or a DVD, placed on the transport tray 54; after the completion ofthe printing, the transport tray is ejected in the direction of thearrow U, thus completing the printing in the horizontal path.

Next, a construction for an anti-jam processing to be performed whenjamming has occurred due to a transport error during U-turn sheetfeeding, duplex transport, or horizontal path transport will bedescribed.

In FIG. 1, the paper guide 23 for guiding the outer side of therecording medium at the time of U-turn sheet feeding and at the time ofduplex transport can be opened and closed using a rotation shaft 23A asthe rotation center. When performing anti-jam processing, the paperguide 23 is opened in the direction of the arrow W, whereby it ispossible to remove the jammed recording medium.

Next, the drive construction of the U-turn sheet feeding roller 6 andthe U-turn transport roller 21 will be described with reference to FIGS.2 and 3.

Reference numeral 41 indicates a U-turn transport roller gear providedon the shaft of the U-turn transport roller 21, reference numeral 42indicates a U-turn sheet feeding roller gear provided on the shaft ofthe U-turn sheet feeding roller 6 and having a one-way clutch mechanism(not shown) transmitting driving force solely in the sheet feedingdirection, reference numeral 39 indicates a drive motor, referencenumeral 40 indicates a motor gear arranged on a motor shaft 39A of thedrive motor 39, reference numerals 50, 52, and 53 indicate pendulumidler gears on which positioning is effected with a pendulum gear holder51 using the motor gear 40 as the rotation center, and referencenumerals 43, 44, and 49 indicated U-turn sheet feeding idler gears fortransmitting driving force from the motor gear 40 to the U-turn sheetfeeding roller gear 42.

Next, a separating operation in U-turn sheet feeding will be describedwith reference to FIG. 2.

When the motor gear 40 rotates in the normal direction, i.e., in thedirection of the arrow A, the pendulum gear holder 51 swings in thedirection of the arrow Y. Then, the pendulum idler gear 50 is broughtinto mesh with the U-turn transport roller gear 41, and the U-turntransport roller 21 rotates in the direction of the arrow C.

At this time, the pendulum idler gear 52 is separated from the U-turntransport roller gear 41 by the swinging in the direction of the arrow Yof the pendulum gear holder 51, and no driving force is transmitted. Atthe same time, driving force is transmitted to the U-turn sheet feedingroller gear 42 through the U-turn sheet feeding idler gears 43, 44, and49, and the U-turn sheet feeding roller 6 rotates in the direction ofthe arrow X, the recording medium being separated to be fed. When therecording medium is fed and reaches the nip portion between the U-turntransport roller 21 and the U-turn transport roller 25, the sheetfeeding operation is completed (FIG. 1).

Next, a transport operation in U-turn sheet feeding will be describedwith reference to FIG. 3.

When the sheet feeding operation is completed, the motor gear 40 isreversed to rotate in the direction of the arrow F; then, the pendulumgear holder 51 swings in the direction of the arrow Z, and the pendulumidler gear 52 is meshed with the U-turn transport roller gear 41, theU-turn transport roller 21 rotating in the direction of the arrow C asin the case of sheet feeding.

At this time, the pendulum idler gear 50 is separated from the U-turntransport roller gear 41 by the swinging in the Z-direction of thependulum gear holder 51, and no driving force is transmitted. On theother hand, driving force is transmitted to the U-turn sheet feedingroller gear 42 through the U-turn sheet feeding idler gears 43, 44, and49; however, due to the above-described one-way clutch mechanism, thedriving of the U-turn sheet feeding roller gear 42 is not transmitted tothe U-turn sheet feeding roller 6, and the U-turn sheet feeding roller 6is brought to a stop.

Next, a two-side printing operation will be described with reference toFIG. 3.

When the motor gear 40 is reversed to rotate in the direction of thearrow F, the U-turn transport roller 21 rotates in the direction of thearrow C. By the rotation of the U-turn transport roller 21 in thedirection of the arrow C, transport for two-side printing is conducted.At this time, the U-turn sheet feeding roller 6 is at rest due to theabove-described drive construction, and no sheet feeding operation isconducted. Otherwise, the operation is the same as the above-describedtransport operation for two-side printing, so that a description thereofwill be omitted.

As described above, commonality is achieved between the transport pathfor U-turn sheet feeding and the transport path for two-side printing,as well as overlapping with the horizontal path, whereby it is possibleto realize a reduction in size and cost.

[Embodiment 2]

In Embodiment 1 described above, the recording medium transportdirection in U-turn sheet feeding and the recording medium transportdirection in two-side printing are the same. In Embodiment 2, therecording medium transport direction in U-turn sheet feeding and therecording medium transport direction in two-side printing are oppositeto each other.

A U-turn sheet feeding operation will be described with reference toFIG. 5.

This embodiment differs from Embodiment 1 in that a paper guide flapper30 is added to the forward end of the paper guide 22. The paper guideflapper 30 has a rotation center 30A, around which it is weakly urgedtoward the paper guide 23. Since the paper guide flapper 30 is urgedwith a low pressure, the recording medium can pass between the paperguide 23 and the paper guide flapper 30. The recording medium fed by theU-turn sheet feeding roller 6 is transported in the direction of thearrow M, and is transported in the direction of the arrow while guidedby the paper guide 23 and the paper guide flapper 30. The operation fromthis onward is the same as that in Embodiment 1, so that a descriptionthereof will be omitted. The construction of the horizontal path forperforming printing on a thick recording medium, such as a CD or a DVD,is the same that of Embodiment 1, so that a description thereof will beomitted.

Next, a two-side printing structure will be described with reference toFIG. 6.

The operation from the U-turn sheet feeding to the surface printingoperation is the same as that in Embodiment 1, so that a descriptionthereof will be omitted. When the surface printing is completed, themain transport roller pair 3 and the ejection roller pair 4 are reversedin rotation, and the recording medium is transported in the direction ofthe arrow R. The recording medium is further transported in thedirection of the arrow b by the main transport roller pair 3, and istransported to the duplex transport portion. At this time, the paperguide flapper 24 moves in the direction of the arrow a, thus securingthe transport path.

Further, conversely to U-turn sheet feeding, the U-turn sheet transportroller 21 rotates in the direction of the arrow e. As a result, therecording medium is transported in the directions of the arrows d and fwhile guided by the paper guide 26, the paper guide flapper 24, thepaper guide 23, and the paper guide flapper 30. Further, the recordingmedium is transported in the direction of the arrow P while guided bythe abutment portion of the paper guide 27 and the paper guide flapper24, whereby the recording medium reversing operation is completed. Atthis time, the paper guide flapper 24 abuts the paper guide 27 with alow pressure, so that the recording medium is allowed to pass. Thetransport operation from this onward is the same as that in Embodiment1, so that a description thereof will be omitted.

[Embodiment 3]

In Embodiment 1, the U-turn sheet feeding mechanism is arranged at aposition separate from the transport path for two-side printing. InEmbodiment 3, the U-turn sheet feeding mechanism is formed in thetransport path for two-side printing, thereby achieving a furtherreduction in size.

A U-turn sheet feeding operation will be described with reference toFIG. 7.

This embodiment differs from Embodiment 1 in that the U-turn sheetfeeding roller 6 is eliminated and that there is added a separationroller 38 adapted to abut the U-turn transport roller 21 to separate therecording medium. In this construction, the U-turn transport roller 21also serves as the sheet feeding roller. Further, there is provided amiddle plate 37 for bringing the recording medium P into press contactwith the U-turn transport roller 21. Through rotation of the U-turntransport roller 21, the recording medium P is transported in thedirection of the arrow M. Then, the recording medium is separated at thenip portion between the U-turn transport roller 21 and the separationroller 38 and is transported in the direction of the arrow N. When theseparation of the recording medium is completed, the middle plate 37retracts in the direction of the arrow g, and moves to a position wherethe next sheet feeding is not conducted. The transport operation fromthis onward is the same as that in Embodiment 1, so that a descriptionthereof will be omitted.

The construction of the horizontal path for performing printing on athick recording medium, such as a CD or a DVD, is the same that ofEmbodiment 1, so that a description thereof will be omitted.

Next, a two-side printing structure will be described with reference toFIG. 8.

The operation from the U-turn sheet feeding to the surface printingoperation is the same as that in Embodiment 1, so that a descriptionthereof will be omitted. When the surface printing is completed, themain transport roller pair 3 and the ejection roller pair 4 are reversedin rotation, and the recording medium is transported in the direction ofthe arrow R. The recording medium is further transported in thedirection of the arrow S by the main transport roller pair 3, and istransported to the duplex transport portion. At this time, the recordingmedium is transported while guided by the paper guide 24A of the paperguide flapper 24 and the paper guide 27. Further, the recording mediumis transported in the direction of the arrow H while guided by the paperguides 27 and 22, and meets the U-turn sheet feeding transport path. Atthis time, the middle plate 37 retracts in the direction of the arrow g,and the separation roller 38 also retracts in the direction of the arrowh, thus securing the transport path. The transport operation from thisonward is the same as that in the U-turn sheet feeding operation, sothat a description thereof will be omitted.

[Embodiment 4]

In Embodiment 1, there is provided a single U-turn transport roller fortransporting the recording medium at the time of U-turn sheet feedingand at the time of duplex transport. In Embodiment 4, two U-turntransport rollers are provided. By providing two U-turn transportrollers, it is possible to avoid overlapping of the horizontal path andthe transport roller, and, in addition to the thick recording medium,such as a CD or a DVD, a thick paper sheet of A4 width can also betransported in the horizontal path.

A U-turn sheet feeding operation will be described with reference toFIG. 9.

This embodiment differs from Embodiment 1 in that there are added asecond U-turn transport roller 22 and paper guides 28 and 29. Further,the position of the paper guide flapper 24 is changed. The recordingmedium fed by the U-turn sheet feeding roller 6 is transported in thedirection of the arrow M, and transported in the direction of the arrowj while guided by the paper guides 22, 23, 28, and 29, and is furthertransported in the directions of the arrows N, I, and P by the secondU-turn transport roller 22. At this time, the paper guide flapper 24moves in the direction of the arrow i to secure the transport path. Thetransport operation from this onward is the same as that in Embodiment1, so that a description thereof will be omitted.

Next, the construction of the horizontal path for performing printing ona thick recording medium, such as a CD or a DVD, will be described.

The paper guide 23 for guiding the outer side of the recording mediumduring U-turn sheet feeding and duplex transport is equipped with theguide hole 23B for guiding the recording medium in the horizontal path.

The paper guide flapper 24 moves in the direction of the arrow i tosecure the transport path of the horizontal path. In the horizontalpath, the recording medium is guided by the paper guides 26 and 27, thepaper guide flapper 24, the paper guides 28 and 29, and the guide hole23B of the paper guide 23. While in Embodiment 1 the recording mediumtransport path in the horizontal path and the U-turn transport roller 21overlap each other, by arranging two transport rollers (21 and 22),there is no overlapping of the recording medium transport path in thehorizontal path and the U-turn transport rollers 21 and 22, so that, inaddition to a CD, a DVD, or the like, a thick paper sheet of A4 widthcan also be transported. Otherwise, the construction of the horizontalpath is the same as that of Embodiment 1, so that a description thereofwill be omitted.

Next, a two-side printing operation will be described with reference toFIG. 10.

The operation from the U-turn sheet feeding to the surface printing isthe same as that in Embodiment 1, so that a description thereof will beomitted. When the surface printing is completed, the main transportroller pair 3 and the ejection roller pair 4 are reversed in rotation totransport the recording medium in the direction of the arrow R. Therecording medium is further transported in the direction of the arrow Sby the main transport roller pair 3, and is transported to the duplextransport portion. At this time, the paper guide flapper 24 moves in thedirection of the arrow K to secure the transport path. Further, therecording medium is transported in the directions of the arrows H, j,and N while guided by the paper guide 27, the paper guide flapper 24,and the paper guides 22, 23, 28, and 29. The transport operation fromthis onward is the same as that of Embodiment 1, so that a descriptionthereof will be omitted.

[Embodiment 5]

In Embodiment 2 described above, a single U-turn transport roller isprovided, and the recording medium transport direction in U-turn sheetfeeding and the recording medium transport direction in two-sideprinting are opposite to each other. In Embodiment 5, two U-turntransport rollers are provided, and the recording medium transportdirection in U-turn sheet feeding and the recording medium transportdirection in two-side printing are opposite to each other.

A U-turn sheet feeding operation and a recording medium transportoperation in the horizontal path will be described with reference toFIG. 11.

This embodiment is the same as Embodiment 4 in that two U-turn transportrollers (21 and 22) are provided, and the same as Embodiment 2 in thatthe recording medium transport direction in U-turn sheet feeding and therecording medium transport direction in two-side printing are oppositeto each other, so that a description of these features will be omitted.

Next, a two-side printing operation will be described with reference toFIG. 12.

This embodiment is the same as Embodiment 4 in that two U-turn transportrollers (21 and 22) are provided, and the same as Embodiment 2 in thatthe recording medium transport direction in U-turn sheet feeding and therecording medium transport direction in two-side printing are oppositeto each other, so that a description of these features will be omitted.

[Embodiment 6]

In Embodiment 2 described above, a pendulum gear is used for drivingforce transmission from the drive motor 39 to the U-turn transportroller 21. In Embodiment 6, a one-way clutch is used instead of thependulum gear. Embodiment 6 will be described with reference to FIGS. 13and 14.

This embodiment differs from Embodiment 1 in that there are two drivingpaths from the motor gear 40 to the U-turn transport roller gear 41. Onepath connects the motor gear 40 to the U-turn transport roller gear 41by way of idler gears 45 and 47. The other path connects the motor gear40 to the U-turn transport roller gear 41 by way of an idler gear 46.The idler gear 47 is formed by a double gear and has a speed reductionmechanism. This makes it possible to reduce the transport speed ascompared with that in the other driving path. Further, it is alsopossible for the double gear of the idler gear 47 to have a speedincreasing mechanism, making it possible to increase the transport speedas compared with that in the other driving path.

Further, the idler gear 45 or 47 is provided with a one-way clutchmechanism (not shown) for transmitting driving force solely in thedirection of the arrow in FIG. 13. Similarly, the idler gear 46 is alsoprovided with a one-way clutch mechanism (not shown) for transmittingdriving force solely in the direction of the arrow in FIG. 14. From themotor gear 40 to the U-turn sheet feeding roller gear 42, drivingconnection is effected by idler gears 43 and 44.

Next, a U-turn sheet feeding operation will be described with referenceto FIG. 13.

When the motor gear 40 is driven in the normal direction to rotate inthe direction of the arrow 1, the idler gears 45 and 47 rotate in thedirections of the arrows, and driving force is transmitted to the U-turntransport roller gear 41, causing the U-turn transport roller 21 torotate in the direction of the arrow C. In this process, due to theone-way clutch mechanism formed in the idler gear 46, no driving forceis transmitted to one driving path to the U-turn transport roller gear41. On the other hand, driving force is transmitted from the U-turnsheet feeding roller gear 42 through the idler gears 43 and 44, and therecording medium is separated and fed. When the recording medium is fed,and reaches the nip portion between the U-turn transport roller 21 andthe U-turn transport roller 25, the sheet feeding operation is completed(FIG. 1).

Next, a transport operation in U-turn sheet feeding will be describedwith reference to FIG. 14.

When the sheet feeding operation is completed, the motor gear 40 isreversed to rotate in the direction of the arrow m; then, the idler gear46 rotates in the direction of the arrow, transmitting driving force tothe U-turn transport roller gear 41. As in the sheet feeding operation,this causes the U-turn transport roller 21 to rotate in the direction ofthe arrow C. At this time, due to the one-way clutch mechanism providedin the idler gear 45 or 47, no driving force is transmitted from theother driving path to the U-turn transport roller gear 41.

Further, while driving force is transmitted to the U-turn sheet feedingroller gear 42 through the U-turn sheet feeding idler gears 43 and 44,due to the one-way clutch mechanism, no driving force is transmittedfrom the U-turn sheet feeding roller gear 42 to the U-turn sheet feedingroller gear 6, which is brought to a stop.

Next, an operation in two-side printing will be described with referenceto FIG. 14.

When the motor gear 40 is reversed to rotate in the direction of thearrow m, the U-turn transport roller 21 rotates in the direction of thearrow C. By the rotation of the U-turn transport roller 21 in thedirection of the arrow C, the transport in two-side printing iseffected. At this time, due to the above-described drive construction,the U-turn sheet feeding roller 6 is at rest, and no sheet feedingoperation is conducted. Otherwise, this embodiment is the same asEmbodiment 1, so that a further description thereof will be omitted.

[Embodiment 7]

In Embodiments 1 and 6 described above, the drive motor 39 is used todrive the U-turn transport roller 21. In Embodiment 7, driving force istransmitted to the U-turn transport roller 21 from the drive motor fordriving the main transport roller pair 3 or the ejection roller pair 4.In this embodiment also, due to the pendulum gear or the one-way clutchmechanism, even if the main transport roller pair 3 or the ejectionrollers 4 make normal and reverse rotation, the U-turn transport roller21 rotates in one direction only.

[Embodiment 8]

In Embodiment 1 described above, a construction in which a commonalityis achieved between the U-turn sheet feeding transport path and theduplex transport path is incorporated into the apparatus main body. InEmbodiment 8, the transport portion for U-turn sheet feeding and duplextransport is formed as a unit, which is detachably mountable to theapparatus main body. Embodiment 8 will be described with reference toFIG. 15.

An apparatus main body 48 is equipped with a mechanism for feedingsheets from above. Reference numeral 31 indicates a sheet feeding rollerfor separately feeding recording mediums, and reference numeral 32indicates a stacking portion where recording mediums are stackedtogether. A recording medium fed by the sheet feeding roller 31 istransported to the main transport roller pair 3 while guided by a paperguide flapper 34 and a paper guide 35. The operations from printing onthe recording medium to sheet ejection are the same as those inEmbodiment 1, so that a description thereof will be omitted. AU-turn-sheet-feeding/duplex-transport unit 56 allows separation betweena section formed by main body frames 36 and 33 of the apparatus mainbody 48 and a section formed by the paper guide portions 23 and 27 ofthe U-turn-sheet-feeding/duplex-transport unit 56. The construction ofthe transport portion is the same as that of Embodiment 1, so that adescription thereof will be omitted.

In effecting the connection of the U-turn-sheet-feeding/duplex-transportunit 56 to the apparatus main body 48, positioning/fixing is effected bya positioning portion (not shown), and the mounting of the unit isdetected by an electric detecting portion (not shown). When the mountingof the unit is detected, printer control is effected through control incorrespondence with U-turn sheet feeding and two-side printing.

[Embodiment 9]

A standard recording apparatus according to this embodiment has amechanism for feeding sheets from above the apparatus main body,functions to perform U-turn sheet feeding, duplex transport, and thetransport of a thick recording medium, such as a CD or a DVD, and,further, a transport path allowing two-side printing on not only a cutpaper sheet, such as an A4 size or letter size sheet but also a smallersize cut sheet such as an L-print size. Further, the recording apparatusof this embodiment has a transport path which allows, even in U-turnsheet feeding and two-side printing, not only the feeding of sheets fromabove but also the transport of a recording medium of high quality thatdoes not easily bend.

The transport path of the recording apparatus of Embodiment 9 will bedescribed with reference to FIG. 16.

As in Embodiment 4, in this embodiment, there are provided two U-turntransport rollers (21 and 22). This makes it possible to secure thehorizontal path for transporting a thick recording medium, such as a CDor a DVD, without involving an increase in the size of the main body,and to arrange the transport rollers at positions corresponding tovarious recording medium widths, such as A4, B5, A5, 2L-print, 4×6 size,postcard, envelope, and L-print size.

Reference numeral 101 indicates a duplex transport roller, which isrotatably set in position in a U-turn transport unit casing 108. AU-turn sheet feeding roller 6 has a semicircular configuration, and isarranged in the duplex transport path in order to achieve a reduction inthe size of the main body. Further, a separation roller 38 in contactwith the U-turn sheet feeding roller 6 and a holder 104 holding theseparation roller 38 are arranged outside the transport path for U-turnsheet feeding and the transport path for duplex transport.

Reference numeral 111 indicates a first detection lever, and referencenumeral 112 indicates a first detection sensor for detecting theoperation of the first detection lever 111. The first detection lever111 is arranged at a position where the transport paths for sheetfeeding from above, U-turn sheet feeding, and duplex transport join, anddetects the leading end and trailing end of a recording medium. Here, athick recording medium, such as a CD or a DVD, is transported so as tobe offset from the first detection lever 111 with respect to the widthdirection of the recording medium. This helps to prevent the thickrecording medium, such as a CD or a DVD, and the first detection lever111 from coming into contact with each other.

Reference numeral 113 indicates a second detection lever, and referencenumeral 114 indicates a second detection sensor for detecting theoperation of the second detection lever 113. The second detection lever113 is arranged in the common transport path for U-turn sheet feedingand duplex transport and in the vicinity of a two-side flapper 110, andperforms detection of the presence/absence and the trailing end of arecording medium during U-turn sheet feeding and detection of theleading end and trailing end of a recording medium during duplextransport. Further, it is also possible to perform detection as towhether or not a recording medium is sticking out of the sheet feedingcassette 5 to block the transport path for duplex transport. In order toprevent the second detection lever 113 from being abruptly caused torotate by the ascent of the middle plate 37 to thereby generate noiseduring U-turn sheet feeding when the middle plate 37 is to be raised bya cam provided on the shaft of the U-turn sheet feeding roller 6, thesecond detection lever 113 is retracted upwards before the middle plate37 and the recording medium P come into contact with each other,restoring the second detection lever 113 so that it may abut therecording medium P after the middle plate 37 has ascended. Due to thisoperation, it is possible to detect the presence/absence of a recordingmedium while preventing generation of noise.

As guide members on the outer side of the U-turn sheet feeding transportpath, there are provided a guide portion 108 a constituting a part ofthe casing 108 of the U-turn transport unit, a guide 23 also serving asan opening/closing portion for anti-jam processing, a lower surfaceportion 117 a of an upper-side sheet feeding unit casing 117, anupper-side sheet feeding guide flapper 34, and a paper guide portion 118supporting a pinch roller of the main transport roller pair 3 androtatably supporting the first detection lever 111. Further, as guidemembers on the inner side of the U-turn sheet feeding transport path,there are provided a guide portion 105 a constituting a part of an innerguide 105 of the duplex transport portion, a paper guide 106 arrangedbetween two U-turn transport rollers 21 and 22, a guide portion 108 bconstituting a part of the U-turn transport unit casing 108, an upperguide portion 109 a of a paper guide 109 downwardly swingable around thecenter axis of a main transport roller 3-1 of the main transport rollerpair 3, and an upper guide portion 24 c of a paper guide 24 rotatablymounted to the paper guide 109 at a center axis portion 24 b. Here, aspace SA above the guide portion 108 b is a clearance portion for a loopwhen performing registration; it is a clearance portion for the S-shapedportion of a recording medium formed during registration by a recordingmedium bending force generated due to the fact that the nip portion ofthe main transport roller pair 3 is arranged so as to be offsetdownstream with respect to the transporting direction of the recordingmedium.

As the guide members on the outer side of the duplex transport path,there are provided a paper guide portion 109 c constituting a part of apaper guide 109 downwardly swingable, a paper guide portion 120 aconstituting a part of a casing base 120 of the recording apparatus, anunder paper guide 103 for anti-jam processing mounted so as to berotatable around a rotation shaft 103 a with respect to the U-turntransport unit casing 108 while rotatably supporting a two-side pinchroller 102 adapted to rotate with the duplex transport roller 101, and atwo-side flapper 110 mounted to the U-turn transport unit casing 108 soas to be rotatable around a rotation shaft 110 a and adapted to effectswitching between the transport path for U-turn sheet feeding and theduplex transport path. Due to this construction, the downstream sidetransport path is the same as the above-described transport path forU-turn sheet feeding. Further, as the guide members on the inner side ofthe duplex transport path, there are provided a lower guide portion 24 dof the rotatable paper guide 24, a lower guide portion 109 b of thepaper guide 109, and a guide portion 105 b of the paper guide 105rotatably supporting the second detection lever 113. Further, to reducethe resistance in the transport of a recording medium, the paper guide105 is provided with a roller 119 which is rotatable.

Next, the transport path in this embodiment will be described.

In the U-turn transport portion, the outer guide has an arcuateconfiguration, whereas the inner guide 106 arranged between the twoU-turn transport rollers 21 and 22 is formed so as to clear inwards. Theclearance portion SB is of a configuration as required for the transportof a highly rigid recording medium by the two U-turn transport rollers.It functions as a clearance portion to be utilized when inward wrappingof the recording medium occurs due to a difference in transporting forcebetween the two rollers or depending on the balance in transportresistance due to the guide portion. If a stationary paper guide portionis provided without securing the clearance portion SB, the followingproblem will be involved: when the trailing end of the recording mediumleaves the first U-turn transport roller 21 on the upstream side, therecording medium, which has been bent by the two U-turn transportrollers, is restored to the original shape by its own rigidity, and getscaught between the paper guide 23 provided on the outer side and thestationary paper guide portion provided on the inner side, resulting inan increase in transport resistance. This leads to a deterioration inimage quality.

FIGS. 17A and 17B are sectional views of the U-turn transport portion.The inner guide 106 arranged between the two U-turn transport rollers 21and 22 is provided with a driven roller 107. As shown in FIG. 17A, whenthe recording medium P is being transported while in contact with theupstream portion of the first U-turn transport roller 21 of the paperguide 23, the recording medium P is not in contact with the drivenroller 107. As shown in FIG. 17B, when the trailing end of the recordingmedium P is detached from the upstream portion of the first U-turntransport roller 21 of the paper guide 23, and leaves the nip portionbetween the first U-turn transport roller 21 and the U-turn transportroller 25, the recording medium P comes into contact with the drivenroller 107. This helps to restrain changes in the behavior of therecording medium P when it leaves the nip portion. Even after thetrailing end of the recording medium P has left the nip portion, therecording medium P is transported while in contact with the drivenroller 107. Here, in order to restrain changes in the behavior of therecording medium when it leaves the nip portion of the U-turn transportroller 21, and to prevent it from constituting a resistance to thetransport of the recording medium afterwards, it is desirable for thedriven roller 107 to be arranged downstream and in the vicinity of thefirst U-turn transport roller 21.

Next, to obtain in the duplex transport path an image equivalent to thatin the U-turn sheet feeding transport path, it is necessary for theU-turn sheet feeding transport path and the duplex transport path tohave the same transport resistance. FIG. 18 is a schematic explanatoryview of the duplex transport path and the U-turn sheet feeding path. Asshown in FIG. 18, to diminish the difference in the reaction forcegenerated by the rigidity of the recording medium, it is necessary, asan imaginary circle UTD of the U-turn transport portion is approached,to at least expand outward by from a common tangent DPP1 to the maintransport roller 3-1 and the imaginary circle UTD of the U-turntransport portion, which constitutes the shortest passage, bringing theU-turn transport path Up and the duplex transport path Dp close to eachother (DPP2 to DPP2OUT). In other words, the angle made by Up and Dp ismade Dθ2, which is smaller than Dθ1 (ideally, Dθ2=0 for the sametransport path). However, when the path: DPP2 to DPP2OUT is adopted, thetransport resistance is rather large in the vicinity of the maintransport roller 3-1. In view of this, a path configuration with a pathbuffer SD is adopted, in which at the position where recording medium Pis conveyed to the duplex transport path by the main transport rollerpair 3, a path DPP2IN is taken and in which after the trailing end ofthe recording medium has left the main transport roller pair 3, a pathDPP2OUT is taken. That is, as shown in FIG. 16, the space SD between theinner guide and the outer guide of the duplex transport path is madesufficiently large. Then, due to the rigidity of the recording medium,when entering the duplex transport path, the path DPP2IN is taken, and,after the trailing end of the recording medium has left the maintransport roller pair 3, the path DPP2OUT is taken. Further, to bringthe U-turn transport path and the duplex transport resistance closer toeach other, a duplex transport roller 101 is preferably provided betweenthe main transport roller 3-1 and the first U-turn transport roller 21,thereby canceling the transport resistance generated on the upstreamside of the duplex transport roller 101.

FIG. 19 is a sectional view showing how a thick recording medium, suchas a CD or a DVD, is transported. As shown in FIG. 19, with the paperguide flapper 24 lowered, the main transport roller 3-1 is reversed,whereby the transport tray 54 with a CD, a DVD or the like placedthereon is transported from the recording medium ejection side. Due tothe rigidity of the transport tray 54, the paper guide 109 suspended bya spring (not shown) is pushed down, and the transport tray is caused topass the portion below the guide portion 108 b of the U-turn transportunit casing 108 and the portion below the second U-turn transport roller22, and is transported to a position in the vicinity of the paper guide106.

Next, the drive row from the drive motor to the U-turn transport rollerwill be described with reference to FIG. 20. The output of the drivemotor 39 is transmitted to a wheel gear 202 through a transmission belt201 from a motor pulley (not shown) press-fitted onto the output shaft39 a, and is further transmitted to U-turn transport roller gears 203and 204 respectively press-fitted onto the U-turn transport rollers 21and 22. The driving force of the U-turn transport roller gear 204 istransmitted through an idle gear 205 to a duplex transport roller gear206 arranged on the shaft of the duplex transport roller 101. That is,when the drive motor 39 rotates in the direction MCCW, the U-turntransport rollers 21 and 22 and the duplex transport roller 101 are allrotated in the direction RCW, in which the recording medium istransported. When the drive motor 39 is rotated in the reversedirection, the U-turn transport rollers 21 and 22 and the duplextransport roller 101 are also rotated in the reverse direction. A codewheel 207, which has printed thereon slits for detecting the recordingmedium transporting amount, that is, the rotating amount of the U-turntransport rollers 21 and 22, is press-fitted, upon accurate positioning,to the wheel gear 202 situated on the upstream side of the U-turntransport roller gears 203 and 204 press-fitted onto the U-turntransport rollers 21 and 22. Then, the slits caused to pass by therotation of the code wheel 207 are detected by an encoder sensor 208.The drive motor 39 is feedback-controlled based on an output signal ofthe encoder sensor 208, thereby controlling the rotation of the U-turntransport rollers 21 and 22 and the duplex transport roller 101, thatis, the transport amount of the recording medium.

Next, the operation of feeding sheets from the sheet feeding cassette 5will be described with reference to FIGS. 21A and 21B and FIGS. 22Athrough 22C. FIGS. 21A and 21B are diagrams illustrating the drivesystem, and FIGS. 22A through 22C are diagrams illustrating how therecording medium is transported.

In FIGS. 21A and 21B, a transport roller output gear 301 arranged on theshaft of the second U-turn transport roller 22 constitutes a sun gear,and driving force is transmitted to a U-turn sheet feeding roller gear304, arranged on the shaft of the U-turn sheet feeding roller 6, bymeans of a swing arm 302, a planetary gear 303, and a friction spring(not shown). Here, reference numeral 309 indicates a controlling unitfor ON/OFF-controlling the locking of the rotation of the swing arm 302;it is connected in driving to the transport roller output gear 301.Depending on the rotating direction and the rotating amount of the drivemotor 39, an opening 309 a appears or disappears. Only when a leverportion 302 a of the swing arm 302 is situated at the opening 309 a, itis possible for the planetary gear 303 and the U-turn sheet feedingroller gear 304 to be meshed with each other. This state is attainedduring the sheet feeding operation by the U-turn sheet feeding roller 6.

The U-turn sheet feeding roller gear 304 is equipped with a cam surface304 a adapted to lower an arm 310 for pushing up the middle plate 37 ofthe sheet feeding cassette 5; through balancing with a spring (notshown) pushing up the arm 310, the operations of raising and loweringthe middle plate 37 are controlled by the rotation of the U-turn sheetfeeding roller gear 304. Also on the opposite side of the U-turn sheetfeeding roller 6, there is arranged a cam 2309 similar to that of theU-turn sheet feeding roller gear 2404, controlling the rising/loweringmotion of the arm 310 and the middle plate 37 from the right and leftsides with the same timing.

In FIG. 22A, the separation roller 38 is equipped with a torque limiter(not shown) so as to allow rotation in one direction only, and isrotatably mounted to a separation roller holder 104. Using a rotationcenter 104 a as a fulcrum, the separation roller holder 104 is broughtinto and out of contact with the U-turn sheet feeding roller 6. Theseparation roller holder 104 is controlled to be brought into and out ofcontact with the U-turn sheet feeding roller 6 by means of a controlgear 305 in mesh with the U-turn sheet feeding roller gear 2404.Further, by a cam (not shown) provided on the U-turn sheet feedingroller 6, a cam follower provided on the duplex transport flapper 110 israised and lowered, whereby the duplex transport flapper 110 is raisedand lowered around the rotation shaft 110 a with the motion of theU-turn sheet feeding roller 6.

When the sheet feeding operation is started, the state of the drivesystem is changed from that shown in FIG. 22A to that shown in FIG. 22B.The middle plate 37, the separation roller 38, and the duplex transportflapper 110 are raised by the above-described mechanism. As a result,the recording medium P in the sheet feeding cassette 5 is fed by theU-turn sheet feeding roller 3. When the rotation of the drive motor 309is continued, and the separation of the recording medium is completed,the drive system is brought into the state as shown in FIG. 21B. Here,the U-turn sheet feeding roller gear 304 has an untoothed portion 304 b.When the untoothed portion 304 b comes to a position where it is opposedto the planetary gear 303, the rotation of the U-turn sheet feedingroller gear 304 stops, and exclusively the U-turn transport rollers 21and 22 and the duplex transport roller 101 rotate, and transport aftersheet feeding and printing by the recording head are performed. At thistime, the state in which the recording medium is transported has beenchanged to that shown in FIG. 22C. The separation roller 38 is placedaway from the transport path, and does not come into contact with therecording medium except during sheet feeding operation, so that it doesnot constitute a resistance to transport. Further, the duplex transportflapper 110 is kept raised during both sheet feeding and U-turntransport, and continues transport. This helps to prevent defectivefeeding or skew feed due to transport resistance attributable to theinfluence of the weight of the duplex transport flapper 110.

Further, the U-turn sheet feeding roller 6 has a semicircularconfiguration; after the feeding of the recording medium P, theclearance portion of the semicircular roller is opposed to the recordingmedium. Due to this construction, the transport path is secured, and thetransport of the recording medium P by the U-turn transport rollers 21and 22 is not hindered. Thus, it is only necessary for the U-turn sheetfeeding roller 6 to be endowed with a sheet transport performance, andthe transport accuracy required of it is not so high.

Next, when the transport is completed, the drive motor 39 is rotated inthe reverse direction in the state shown in FIG. 21B. A transport rolleroutput gear 306 arranged on the shaft of the U-turn transport roller 21constitutes a sun gear, and driving force is transmitted to a controlgear 305 by a swing arm 307, a planetary gear 308, a friction gear (notshown), and a planetary gear 2408. The control gear 305 has an untoothedportion 305 a, and is rotated until the planetary gear 308 comes to aposition where it is opposed to the untoothed portion 305 a. Further,the U-turn sheet feeding roller gear 304 also rotates, and the untoothedportion 304 a is removed from the position where it is opposed to theplanetary gear 303, so that sheet feeding operation is again possiblethrough the next normal rotation of the drive motor 39 (i.e., the drivesystem is restored to the state as shown in FIG. 21A). Here, through camoperation due to the rotation of the U-turn sheet feeding roller gear304, the duplex transport flapper 110 is lowered, making it possible tosecure the duplex transport path (i.e., the drive system is restored tothe state as shown in FIG. 22A). In this state also, due to thesemicircular clearance portion of the U-turn sheet feeding roller 6, theU-turn transport path and the duplex transport path are secured.

Due to the above construction, despite the fact that the U-turn sheetfeeding roller 6 and the separation roller 38 are situated in the duplextransport path, they do not come into contact with the recording mediumduring U-turn transport and duplex transport except during U-turn sheetfeeding operation due to the semicircular configuration of the U-turnsheet feeding roller 6 and the movement of the separation roller 38 awayfrom the transport path. Thus, even if the printing ink on the surfacehas not been dried yet, there is no fear of ink, etc. being transferredto the U-turn sheet feeding roller 6. Further, it is possible tosuppress wear of the U-turn sheet feeding roller 6.

Next, the duplex transport will be described with reference to FIGS. 23Aand 23B.

As shown in FIG. 23A, after the completion of printing on the obverseside of a recording medium, the paper guide flapper 24 is raised by aswitching mechanism (not shown) to secure the entrance to the duplextransport path. Then, by rotating the main transport roller 3-1 in thereverse direction, the recording medium P the obverse side of which hasundergone printing is transported to the duplex transport path below. Atthis time, the drive motor 39 is also rotated in synchronism therewith,whereby the recording medium is transported to the duplex transportroller 101 and the U-turn transport rollers 21 and 22. The seconddetection lever 113, arranged between the duplex transport roller 101and the U-turn transport roller 21, detects whether the recording mediumP is being transported or not.

Here, when the passage of the recording medium P cannot be detected bythe second detection sensor 114, a paper jamming error display is given,calling attention for the necessity of removing the jammed recordingmedium. As the anti-jamming means, the sheet feeding cassette 5 is drawnout, and the paper guide 103 is opened in the direction JA, whereby thepress contact of the two-side pinch roller 102 with the duplex transportroller 101 is canceled, making it possible to remove the jammedrecording medium P. The paper guide 103 is suspended up above by aspring (not shown), and, when released by the user, returns to theoriginal position, where it does not hinder the insertion of thecassette. In this way, a jam processing opening that can be opened andclosed is provided between the sheet feeding cassette and the duplextransport path, whereby jamming can be coped with without using any suchlarge-scale jam processing mechanism as would causeattachment/detachment of roller and units.

Next, when, as shown in FIG. 23B, the leading end of the recordingmedium P having passed the second U-turn transport roller 22 is detectedby the second detection lever 111, the trailing end of the recordingmedium P has already passed the main transport roller pair 3. Then, thepaper guide flapper 24 is lowered by a switching mechanism (not shown),and the main transport roller pair 3 is switched from reverse to normalrotation, causing the U-turn transport rollers 21 and 22 and the duplextransport roller 101 to make normal rotation, whereby the recordingmedium P is transported to the main transport roller pair 3 and printingbecomes possible.

At this time, an opening 309 a of a control ring unit 309 is closed. Alever portion 304 a of a swing arm 304 is obstructed by the control ringunit 309, and the U-turn sheet feeding roller 6 is not driven. In thisstate, reverse side printing is performed, and the recording medium isejected. When two-side printing has been completed or when the trailingend of the recording medium has passed the second U-turn transportroller 22, the opening 309 a of the control ring unit 309 is opened, andthe apparatus is made ready for sheet feeding.

Due to the above construction, it is possible to realize, with a simplestructure, sheet feeding from the upper portion of the main body, U-turnsheet feeding, duplex transport, and the transport of a thick recordingmedium, such as a CD or a DVD. Further, this construction allowstransport of recording mediums of various sizes, and it is possible totransport with high accuracy a high quality recording medium that doesnot easily bend even in the case of U-turn sheet feeding or duplextransport.

According to the above embodiments of the present invention, it ispossible to provide a recording apparatus that helps to achieve areduction in size and cost.

This application claims priority from Japanese Patent Application Nos.2003-382533 filed Nov. 12, 2003 and 2004-238446 filed on Aug. 18, 2004,which are hereby incorporated by reference herein.

1. A recording apparatus comprising: a sheet feeding roller forreversing and feeding a recording medium; a main transport roller fortransporting the recording medium on an upstream side of a recordinghead; a reversing mechanism for turning the recording medium upsidedown; a first transport path for transporting the recording medium fromthe sheet feeding roller to the main transport roller; a secondtransport path for transporting the recording medium in the reversingmechanism, the second transport path sharing a portion thereof with thefirst transport path; a third transport path arranged in the portionshared by the first and second transport paths; and a separation rolleradapted to abut the sheet feeding roller to separate the recordingmedium, wherein during sheet feeding, the sheet feeding roller and theseparation roller are in contact with each other, and when the recordingmedium is to be turned upside down, the sheet feeding roller and theseparation roller are separated from each other.
 2. A recordingapparatus according to claim 1, further comprising a common transportroller provided inside the first transport path and the second transportpath.
 3. A recording apparatus according to claim 2, wherein the commontransport roller and the third transport path overlap each other.
 4. Arecording apparatus according to claim 1, wherein the sheet feedingroller has a semicircular configuration.
 5. A recording apparatusaccording to claim 1, further comprising a common guide means common tothe first transport path and the second transport path, for guiding therecording medium.
 6. A recording apparatus according to claim 5, whereinthe common guide means is opened to an exterior of the recordingapparatus for anti-jam processing.
 7. A recording apparatus according toclaim 1, further comprising a movable paper guide arranged at a positionwhere the second transport path and the first transport path join eachother, wherein a switching operation is conducted such that the paperguide is placed at a lowered position when the recording medium is to beturned upside down and is placed at a raised position when the recordingmedium is to be fed by the sheet feeding roller.
 8. A recordingapparatus according to claim 7, wherein the switching operation isconducted in synchronism with the sheet feeding operation.
 9. Arecording apparatus according to claim 7, wherein the position of thepaper guide is switched according to a kind of recording medium.
 10. Arecording apparatus according to claim 1, further comprising a transportroller provided in the second transport path and between the maintransport roller and the sheet feeding roller.
 11. A recording apparatusaccording to claim 1, wherein the second transport path expandsoutwardly from a common tangent formed by the main transport roller andthe first transport path.
 12. A recording apparatus according to claim1, further comprising a space provided in the second transport path, foreffecting a change between a state in which the recording medium isnipped by the main transport roller and a state in which the recordingmedium has left a nip of the main transport roller.
 13. A recordingapparatus comprising: a U-turn sheet feeding roller for reversing andfeeding a recording medium; a main transport roller for transporting therecording medium on an upstream side of a recording head; a reversingmechanism for turning the recording medium upside down; a firsttransport path for transporting the recording medium from the U-turnsheet feeding roller to the main transport roller; a second transportpath for transporting the recording medium in the reversing mechanism,the second transport path sharing a portion thereof with the firsttransport path; a third transport path arranged in the portion shared bythe first and second transport paths and adapted to transport arecording medium of high rigidity; and a movable paper guide arranged ata position where the second transport path and the first transport pathjoin each other, wherein a switching operation is conducted such thatthe paper guide is placed at a lowered position when the recordingmedium is to be turned upside down and is placed at a raised positionwhen the recording medium is to be fed by the U-turn sheet feedingroller.